Must be 5 years since i last did any sulphuric anodising and at that was rather hit and miss.

The main problem at time was gaining information which seemed a highly guarded secret around 2001. There were only three sites that gave a how to but every one left something out or even told porkies (lies.)All were different including voltages, acid mix, duration and to my bug bear the contact with part to be anodised.

Most recommend an aluminium wire wedged in to the part, for me a breakdown wthin 2 minutes every time even threaded in. The only method short of trying titanium was aluminium 6082 wedge shaped and tightly screwed in to a hole before and after chemical cleaning with hydrochloric acid.

Have even done hard anodising twice but couldnt repeat next time.

For me 17 to 19% sulphuric mix around 13.6 volts measured in hours. Many can do this in minutes.

One thing i did have to figure out was the dye needed warming up but not too much to seal the part. Tryed all dyes i could gey my hands on, literally nothing worked except the powder the pros use.

Thinking back and may be another porky after dipping in colour for a period of time, it was supposed practice to then boil the part in water to seal the colour. Seems now i should have used acetate.

Over the years did have a few parts come out quite professional.Heres a bead blasted itemCome out a bit matt this one.Bit matt this one blue tint opaque most come out purple to brown

One of these days i will get it up and running again, got two PSU 0-30V ones digital twin output the other a backup an analogue from Maplins.

I have been wanting to do anodizing. I make quite a few motorcycle parts that would look good anodized.

I haven't found enough precise info to give it a shot (haven't looked hard enough yet either). One site (got it bookmarked somewhere) offered up a booklet for cheap. I just may go ahead and get it. Sometimes I need things spelled out for me!

A quick question to those in the know. I've seen mention (online) of using DI water for all of the rinse steps in between all operations. Other places just talk about rinsing with water and do not specifically mention DI water.

Do you (anyone) feel that using, specifically, DI water is necessary to get high quality finishes without blotches / variation, or is this just a bit of bad info or specific to certain dyes, etc...?

-Thanks, Kenneth

I have seen the same thing. Some mention DI others don't. Any answers?

...Always and its ALWAYS, add acid to water, never the other way round....

Thanks for the info Robert. Now why add acid to water? Is it because if you add water to acid, the risk of acid splash back is greater?

Thats the simplest reason and probably the best one, term escapes me but acids can react with water and kinda boil back at ya. Easy way to avoid is just always add acid to water. I've played with sulphuric and hydrochloric enough to gain a bit of respect for em. There reasonable safe enough long as some care in handling is observed. Easy enough for anyone who wants to venture to do a google and read up on em.

I've done a few bits of ruff'n'ready anodising over the years. Being a cheapskate, I used caustic soda (lye) from the supermarket to clean and etch a satin finish on the parts, and acid decanted from dead car batteries begged from the local battery replacement place diluted 1:1 with water as the electrolyte.

I already had a 0-30v, 20A power supply; not constant current, so I had to turn up its wick every now and again over the half-hour or so that the process took. The electrical connection was via a bit of aluminium rod threaded into a hole in an inconspicuous place on the parts, and sealed in with a fillet of sealing wax.

The resulting surface, after boiling to seal the pores, looked fine and was certainly more durable than the raw aluminium.

Experiments using fabric dye for colouring all failed; I reckon the proper dyes are needed.

It worked very well - especially the second time. I used an organic dye and that was great, better than the blue dye I posted about that looked washed out. The other piece has been floating around my house for the last year and the colour has fast well. I`d certainly give it another go next time I have something to anodise. Infact, I`ll make a point of it with my next ally part.

Regarding adding acid to water:

Sulphuric acid will "protonate" water. It`ll give a H+ ions (protons) to H2O to form H3O+. This is exothermic and gives out lots of heat. By adding the acid to the water, you are making the acid the limiting reactant (the reaction is in equalibrium which favours/"likes" protonating water (and therefore giving this violent exorthermic reaction)). Adding acid to water - the excess water is almost acting as a heat sink to dissipate the energy. Adding water to the acid (which you shouldn`t do) - with acid being more viscous (as well as all the equilibrium jazz above), they have less kinetic energy and so when the reaction occurs the energy is preferentially transfered to the water (lower Mr (molecular weight) and more kinetic energy) which causes it to boil and spit everywhere...!! ..... or so I believe .... if I`m wrong, I`ll go and hide in the corner. Sounds good though doesn`t it??

Chris, do the organic dyes tend to come from school store cupboards, or are they commonly available?

Andy

Hit him Chris - he's calling you a thief!

FIGHT! FIGHT! FIGHT!

- AndyF -->

Errrr, errrr ...

no only joking - I did try some azo dyes which I made (so no not available) but the best I found was the blue is it Dylon blue? I got a packet from Wilkinsons for next to nothing and it binds just fine. I then heat sealed it. I tried a food dye and that was rubbish.

Regarding using deionised water - this is pretty much an electrolysis setup and so if you have any minerals dissolved in the water they could potentially be deposited on your metal work surface causing the oxidation of the ally layer not to form properly / not bind properly. You`ll end up with areas that have not anodised correctly. Does anyone know the difference between deionised and water produced via reverse osmosis ? I don`t know the difference there and would like to...

no only joking - I did try some azo dyes which I made (so no not available) but the best I found was the blue is it Dylon blue? I got a packet from Wilkinsons for next to nothing and it binds just fine. I then heat sealed it. I tried a food dye and that was rubbish.

Regarding using deionised water - this is pretty much an electrolysis setup and so if you have any minerals dissolved in the water they could potentially be deposited on your metal work surface causing the oxidation of the ally layer not to form properly / not bind properly. You`ll end up with areas that have not anodised correctly. Does anyone know the difference between deionised and water produced via reverse osmosis ? I don`t know the difference there and would like to...

Chris

Thank goodness! I can stop eating this bloody spinach

Dunno about de-ionised water, Chris. I just used very second-hand battery acid diluted with corporation pop straight from the kitchen tap. Coming from the Lake District, it was very soft but there were probably lots of other ions swimming around in it.

I've found a dial I anodised,and it didn't come out too badly:

To forestall criticism, I know the marks aren't very evenly spaced; should have hung a bigger weight from the lathe chuck to take up the backlash in the geartrain needed to give 84 divisions (don't ask what for!).

Dylon was the fabric dye I experimented with, but it didn't come out patchy; it just didn't really "take" at all.

Both are linear PS units. I make sure mine is never where the fumes from the anodizing can get to it and I have a diode in line to make sure current never reverses in the tank for some reason.

Once we figure out the weted surface area of you largest parts we can figure out how big a supply you need.

Edited to point to the correct PS I am thinking about going to....thanks Kenneth...the switching Power Supplies don't seem to be holding up well for anodizing or plating...I didn't pay attention to the part number and linked to a switching one...

This is a (Clairiant) Sanodal Deep Black MLW...if you start with a nicely polished reflective finish you can get a nice wet looking black from it. This part was

The part is 55.9 sq inches. I wanted to be as close to 15 ASF as possible so I set the PS at 5.8 amps and set my timer for 48 minutes. The ano tank temp was 80 degress. It spent 20 minutes in the dye and 20 minutes in the sealer.

I will probably stick with 12 ASF and tank temp at 75 degrees for an hour...

I tried it a few years ago, and have meant to do some more, but other projects kinda got in the way.

Mine was a very low tech set-up, an automotive battery charger, RIT fabric dye from the supermarket, and Lye drain cleaner. For acid I used new automotive battery acid (for those of us stateside, you can (or at least could then) buy a gallon container of it from NAPA).

I never got the bits I wanted black to come out very well, apparently thats a common problem with fabric type dyes. Here's a pic of probably my best result, this is RIT dye and everything red I did came out well. This is a mandrel for installing a caged needle roller bearing:

That looks very good. I did have a few successful runs wih rit dye and non adjustable supplys. Unfortunately it was after stripping the same part several times and getting lucky with the second or third try.

Bob i have one of those digi PSU's twin output 0-30V 0-10A but can bridge. Sure theres a 5V dedicated output to.Although mine doesnt have that name on it it looks very very similar and has packed up twice.Give it a thorough check over first.

Very nice run down and it deserves more of a reply than I can squeeze out this evening.

I think you have enough facts about your parts. You will no doubt end up in good shape.

The 6061 and 7000 series won't give any trouble... The unknown gummy stuff will take some test runs but it looks like you are very organized. Keeping track of all the parameters in your test runs will help you figure out what will and wonít work.

Considering all the long hours you have put into this project itís got to be a scary step for you to take.

You might want to experiment with ASF when you get started. The lower the ASF the easier it is to control the tank temp. ButÖI have found the lower the ASF the softer the final ano finish is. You might very well be satisfied with your parts at a lower temp, and not have to worry about cooling the ano bath.

BTW....our team at work went out to lunch today and I got on the site with my Droid and passed it around for everyone to see your robot studio....I can tell you we didn't end up talking about work. They were all totally blown away with our setup and work.

I need to talk to you sometime about the CNC mill...I had a Anilam rep out to my shop last year and he gave a demo and quote to convert my mill. I just can't justfy the expense at this point.

I sit behind a computer desk all day for a real job. If I ever do buy one or change mine over it will need to be because it will speed my way to retirement...lol.